A friendly tone has suddenly descended on Washington. This past Wednesday, President Obama hosted a dozen Republican senators for a dinner that was later described as “jovial.” Then he lunched with the GOP’s budget hawk, Rep. Paul Ryan of Wisconsin. In coming days, Mr. Obama plans to go to Capitol Hill for more informal conversations with Republicans.

Such old-style civility has been scarce along Pennsylvania Ave. Sound-bite barbs – often personal – have become the norm. Last year, most voters found the election a “frustrating experience,” according to a Pew poll. More than two-thirds saw an increase in “negative campaigning and mudslinging” rather than a discussion of issues.

“It’s going to take a while to build the kind of confidence and trust that’s needed,” Sen. Tom Coburn (R) of Oklahoma said on MSNBC after the dinner with Obama. “If you’ve had years of having somebody put their finger in your eye and question your motivations and ascribe to you things that aren’t accurate, that takes some healing.”

Tone matters as much as substance in almost any relationship – politics, business, or marriage – and for good reason. Tone can alter substance, a truism that elected leaders often forget. Two recent studies help make the case.

In a new book, “Making Hope Happen,” Shane J. Lopez, a Gallup senior scientist and a University of Kansas professor, relied on extensive research to find that employers who actively instill an attitude of hope in their workers have seen a 14 percent increase in productivity. For students given a hopeful outlook at school, there is a 12 percent rise in academic achievement.

The other study is more pertinent to Washington. Published in the Journal of Computer-Mediated Communication, it shows the effects of reading nasty “reader comments” on a website.

Researchers at the University of Wisconsin-Madison and George Mason University asked two groups of about 1,000 each to read a blog that they were told was a scientific discovery. The discovery was actually fiction, as were the reader comments at the end. In one blog, the comments were civil in tone with both support of the discovery and warnings of its risks. For the other, the comments were mostly rude and name-calling, using such words as “idiot” and “stupid,” and with a similar balance in content.

Those who read the negative, ad hominem comments later had a negative impression of the scientific discovery and were polarized. The other group had a favorable reaction to the news.

The researchers called this tendency to be influenced by uncivil comments “the nasty effect.” That’s a perfect phrase for the political tone in Washington and may explain why so little gets done in Congress. Who wants to compromise with someone making personal attacks?

Many Web publications still contend with nasty comments on stories. Moderate them? Bar them? Or just let ’em rip? The choice can influence the tone of an online site, which in turn might effect its substance.

If Obama and the GOP are now trying a friendlier tone, then it signals the potential for a deal on tough issues, such as the debt. Both sides now seem more guarded in what they say of each other. Such decorum has a payoff.

In architecture, it is said that form follows function. But in politics, function can follow form, as in the “good form” of adopting social graces toward one another.